Remove flux and luminosity attributes for now, and finish renaming analysis properties
Added a sub-module that deals with flux conversions
Implemented Fnu per beam
Made tests independent of astropy.units version (which removes parentheses in Astropy 0.3 if denominator only has a single unit)
Re-implemented flux properties and only warn when necessary about using default meta-data values.
Tidied up analysis: warnings for meta-data are only raised when the values are needed and the defaults are used, exceptions for strict meta-data are only raised when needed, Metadata class(es) now implement type checking, and more of the analysis properties are returned as quantities.
Show units in printed table output
x_cen, y_cen, and v_cen are now explicitly in pixel coordinates if no WCS is specified
Make it so that rather than defaulting to u.pixel in the metadata, u.pixel is used if the spatial_scale is missing - this leads to less confusing errors - e.g. 'spatial_scale is needed' rather than 'spatial_scale should be an angle' (the latter will be confusing if the user hasn't set the spatial_scale at all). Also improve consistency of variable naming in flux calculation compared to the rest of the analysis code.
Fix bug in calculation of beams_per_pixel
Merge pull request #54 from astrofrog/analysis-improvements

Remove flux and luminosity attributes for now, and finish renaming analysis properties